Arrangements which provide a degree of flexible power allocation among multiple power rails in computer systems, in a manner to permit the sharing and exchange of power across multiple rails. The drawer sled is formed with a drawer cavity that is sized and shaped to receive a food patty. The inner barrel assembly may comprise multiple, sponge-lined inner tube sections and may also include a near-bit swivel assembly. The switcher control circuit uses the ILDO value and the ISWITCHER value to control an amount of current that is provided by the switcher circuit. A binary coded signal for identifying the interchangeable lens is formed from the output signals of the light receivers.